My new job includes year five English (2,4)
I believe the answer is:
by jove
'my' is the definition.
(both are expressions of surprise)
'new job includes year five english' is the wordplay.
'new' is an anagram indicator.
'includes' means one lot of letters goes inside another.
'year' becomes 'y'.
'five' becomes 'V' (Roman numeral).
'english' becomes 'e' (abbreviation).
'job' with letters rearranged gives 'bjo'.
'bjo' going around 'y' is 'byjo'.
'byjo'+'v'+'e'='BY JOVE'
(Other definitions for by jove that I've seen before include "Well, I'll be blowed!" , "Old exclamation of surprise invoking Jupiter" , "Good God!" , "Good gracious!" , "Crikey!" .)